The Yamato-type (CY) carbonaceous chondrite group: Analogues for the surface of asteroid Ryugu?
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Issue date
20/08/2019Submitted date
2019-11-20Subject Terms
Carbonaceous chondriteAqueous alteration
Thermal metamorphism
Asteroids
Meteorites
Ryugu
Hayabusa-2
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Show full item recordAbstract
We report new mineralogical, petrographic and noble gas analyses of the carbonaceous chondrite meteorites Y-82162 (C1/2ung), Y-980115 (CI1), Y-86029 (CI1), Y-86720 (C2ung), Y-86789 (C2ung), and B-7904 (C2ung). Combining our results with literature data we show that these meteorites experienced varying degrees of aqueous alteration followed by short-lived thermal metamorphism at temperatures of >500 °C. These meteorites have similar mineralogy, textures and chemical characteristics suggesting that they are genetically related, and we strongly support the conclusion of Ikeda (1992) that they form a distinct group, the CYs (“Yamato-type”). The CY chondrites have the heaviest oxygen isotopic compositions (δ17O ˜12‰, δ18O ˜22‰) of any meteorite group, high abundances of Fe-sulphides (˜10 ‒ 30 vol%) and phosphates, and contain large grains of periclase and unusual objects of secondary minerals not reported in other carbonaceous chondrites. These features cannot be attributed to parent body processes alone, and indicate that the CYs had a different starting mineralogy and/or alteration history to other chondrite groups, perhaps because they formed in a different region of the protoplanetary disk. The short cosmic-ray exposure ages (≤1.3 Ma) of the CY chondrites suggest that they are derived from a near-Earth source, with recent observations by the Hayabusa2 spacecraft highlighting a possible link to the rubble-pile asteroid Ryugu.Citation
A.J. King, H.C. Bates, D. Krietsch, H. Busemann, P.L. Clay, P.F. Schofield, S.S. Russell, The Yamato-type (CY) carbonaceous chondrite group: Analogues for the surface of asteroid Ryugu?, Geochemistry, Volume 79, Issue 4, 2019, 125531, ISSN 0009-2819, https://doi.org/10.1016/j.chemer.2019.08.003.Publisher
Elsevier BVJournal
GeochemistryType
Journal ArticleItem Description
2019 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). The attached file is the published pdf.NHM Repository
ISSN
0009-2819ae974a485f413a2113503eed53cd6c53
https://doi.org/10.1016/j.chemer.2019.08.003
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